1. Field of the Invention
The present invention is directed to a method for preparing metal phosphide nanocrystals from a phosphite compound, and a method for passivating a nanocrystal core with the same. More specifically, the present invention relates to a method for producing metal phosphide nanocrystals and a method for passivating a nanocrystal core, which can be conducted under more controlled conditions via the introduction of a phosphite compound as a phosphorous precursor.
2. Description of the Related Art
Nanocrystals exhibit electrical, magnetic, optical, chemical and mechanical properties that are distinguished from those of bulky substances. Since the properties of nanocrystals are readily controllable depending upon the size and composition of the nanocrystals, there has been extensive interest in nanocrystals. Based on their luminescent and electrical properties alone, nanocrystals can be utilized in a variety of applications including light-emitting and light-receiving devices, solar cells, sensors and lasers.
Vapor deposition processes, including metal organic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE), have been used to prepare nanocrystals. In recent years, there have been a number of studies conducted to investigate the preparation of semiconductor nanocrystals using a wet chemistry method wherein a precursor material is added to a coordinating organic solvent in order to grow the nanocrystals to a desired size.
As the crystals are grown, the organic solvent is naturally coordinated to the surface of the nanocrystals, thereby acting as a dispersant to adjust the crystals to a nanometer-scale level. The wet chemistry method has advantages in that nanocrystals of a variety of sizes can be uniformly prepared by appropriately controlling the concentration of precursor materials used, the type of organic solvents used, as well as the preparation temperature and time. In particular, since Group II-VI compound semiconductor nanocrystals can emit light in the visible range and, since they can be prepared in a simple manner as compared to Group III-V compound semiconductor nanocrystals, they are actively under study.
Since Group III-V compound semiconductor nanocrystals have a covalent bond, they exhibit superior stability and relatively low toxicity as compared to Group II-VI compound semiconductor nanocrystals that have an ionic bond. However, Group III-V compound semiconductor nanocrystals have disadvantages associated with their synthesis such as, for example, a long synthesis time and a limited number of potential precursors.
In particular, synthesis methods for metal phosphide nanocrystals (e.g., indium phosphide (InP) or gallium phosphide (GaP)) are being actively studied. According to prior art wet chemistry methods, trimethylsilyl phosphine (“(TMS)3P”) is the only phosphorus precursor used. However, (TMS)3P has a very high reactivity, thus making it difficult to control a reaction under predetermined conditions.
Accordingly, there is an increasing demand for a wet chemistry synthesis method that enables the preparation of metal phosphide nanocrystals under more controlled conditions.